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What Are the Long Term-Effects of Disinfecting School Buses?

Unprecedented. This word has become all too familiar during the current COVID-19 pandemic, and while most of us are growing weary of the current crisis and hearing this word, it is still an appropriate way to start this article.

As our society struggles to return to some type of normalcy, we are seeking new ways to protect public spaces and transportation, especially the school buses that take our children to and from school. In an effort to prevent the spread of COVID-19 and other diseases, many approaches are being developed to disinfect school buses, ranging from manually wiping down high-traffic touch areas with disinfectant to a variety of different spray options. Each has pros and cons that cannot be covered in this short article, but there are some general considerations to share.

There are a variety of different spray systems available, including small, battery-operated, hand-held foggers, to backpack sprayers, and permanently mounted automated systems. Each of these systems are designed to spray some type of disinfectant to kill any pathogens that could be found in a bus or classroom. It is incumbent upon the school to do its homework and consider all angles of a system before purchasing it. Any systems that relies heavily on the human element for applications could result in inadequate coverage and potentially be labor (hence cost) intensive.

But more importantly than choosing the delivery system, we should first consider the safety of the disinfectant itself. There are least three questions that need to be asked: What are the long terms effects on people? What are the long-tern effects on safety components of the bus? Does the disinfectant kill pathogens as claimed?

Let’s consider each of these questions individually.

Long-Terms Effects on People

Prior to this unprecedented time, regular disinfecting of buses and public spaces may not have occurred consistently. (While many would say, “There was no need.” Think about the reduction in the spread of the common cold, flu or stomach viruses, if routine disinfection occurred.) As a result, the impact of human exposure on an occasional basis was not considered, and why would it have been? Most disinfectants that are registered with the U.S. Environmental Protection Agency (EPA) regardless of type, state that they are safe below a given concentration, so a once-per-month application is not a concern. However, if one takes the time to look at the active ingredients in many of the chemical-based disinfectants currently available, exposure to higher concentrations of the active ingredient can lead to a myriad of unwanted side effects. Studies on human exposure to these chemicals contained in a fine mist or fog several times a day or residue build up have yet to be conducted. Before now, there was simply no urgency to do so.

Long-Term Effects on Bus Components

As discussed previously, the amounts of disinfectants being used currently have never been applied in the volumes and frequency with which they are now. Just as the active ingredients in high concentrations have potential implications on human health, these same concentrations have the potential to be corrosive. Again, infrequent use at EPA-approved concentrations does not cause a concern on the surface integrity of seatbelts, seats, or seat fasteners. But the impact on the integrity of these components exposed to the amounts currently being sprayed is an unknown.

Editor’s note: Refer to the owner’s manual of any components used on school buses to find manufacturer recommendations for cleaning and disinfecting.

Related: Is Cleaning School Buses as Easy as Flipping a Switch?
Related: (STN Podcast E53) Unexpected Improvements: COVID-19 Procedures Benefit Student Transportation
Related: Are you concerned about the long-term effects of frequent cleaning on school bus seats and other equipment?
Related: PURELL Brand Strongly Positioned to Support Safe Reopening of Schools

Does the Disinfectant Kill Pathogens as Claimed?

At the onset of the pandemic, I participated in an independent test on several disinfectants that claim to kill bacterial and viral pathogens. Several had active ingredients commonly used in a wide array of commercially available disinfectants and were tested at the “ready to use” concentration supplied by the manufacturer. We conducted our tests at the undiluted concentration and several serial dilution concentrations in order to test effectiveness if it were accidentally diluted. The testing was conducted with several difficult to kill bacterial pathogens like Salmonella, Staphylococcus (MRSA), and Pseudomonas. We only found two products that performed as well as the label claim, even when diluted, and were surprised with the results obtained with others. One disinfectant failed to kill any of the bacteria even after 24 hours of exposure to the recommended concentration.

Based on our observations, it is imperative that school districts conduct a thorough due diligence on a system or disinfectant before capital outlay. It is important to use resources wisely and even more important to use products that are safe and effective in protecting our children.

Editor’s note: Visit to access a Food and Drug Administration online database that contains “Warning Letters” sent to companies found to have made misleading marketing claims about the effectiveness of their products in killing viruses.

Dr. Richard Cooper is the chief science officer for Clean Spray Technologies, which manufacturers plant-based disinfectant spray and fogging systems. He received his Ph.D. in medical microbiology from the University of Georgie College of Veterinary Medicine. Cooper has spent the majority of his career developing methods to prevent diseases caused by pathogenic bacteria.

Editor’s Note: As reprinted in the March 2021 issue of School Transportation News. 


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